Originally Posted by Dave_3
Higher pressure, less easily deformed overall so will ride on its edge more.
Increasing pressure reduces shoulder wear on run-flats, as you run on the crown of the tyre, not so much on the stiff sidewalls.
One of the reasons run-flats wear so bad on the shoulders is the tyres take longer to warm up to full working pressure, so more time at lower than ideal pressure. Lots of short runs make the situation even worse, tyres hardly ever run at optimum working pressure. I personally run a couple psi higher winter time, just to compensate for this fact and reduce shoulder wear.